All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Neural implants have emerged over the last few decades as a possible means to interact directly with our nervous system. By bridging the gap between our nervous system and the external environment, a neural implant system can potentially replace neural functions and treat neural disorders. Electrodes are one of the key components of neural implant systems that allow the electrical stimulation and recoding of activity of our neurons. The advancement of Micro-Electro Mechanical Systems (MEMS) has made the realization of microelectrodes possible. The key advantages of using MEMS fabricated electrodes over traditional metal wire electrodes are batch fabrication, improved reproducible geometry and electrical characteristics, smaller feature size, and the capabilities for on-chip circuitry.
Although microelectrodes have demonstrated success, their short lifespans are a barrier to clinical practicality. Microelectrodes typically last less than a year due to cellular responses upon implantation. Within the last decade there have been efforts to include fluidic channels in electrodes. The incorporation of fluidic channels would not only allow for simulation electrophysiological measurements but also the capability to delivery drugs that enhance nerve regeneration and prevent reactive cellular response.
Microelectrodes with fluidic delivery capabilities could not only prevent these reactive cellular responses but also allow for electrophysiological measurements and the capability to delivery drugs that enhance nerve regeneration. Fluidic channels were fabricated in the traditional Michigan probes by using shallow boron diffusion to define the channel mask, reactive ion etching to etch the channel, ethylene diamine and pyrocatecho to form a continues flow channel by undercutting the mask, and growing and depositing dielectrics to seal the channel. Other groups have similarly used sacrificial layers and sealants to construct fluidic neural probes. An alternative to sealing the channel with dielectrics or using sacrificial materials is bonding the channel roof to walls of microchannel. The limitation of bonding technique occurs from low adhesion strength, poor alignment. Fluidic channels fabricated with sacrificial layers and dielectric sealing methods are limited by deliverable volume. The challenge in multielectrode fabrication efforts today is developing processes that allows for scalability, reproducibility, and precision dimension control.